Test key array

ABSTRACT

The present invention provides a test key array including a lower conductive pattern, and the lower conductive pattern includes a plurality of first L-shaped traces parallel to each other, an upper conductive pattern, where the upper conductive pattern includes a plurality of second L-shaped traces parallel to each other, the lower conductive pattern crosses to the upper conductive pattern, and a plurality of cross regions are defined between the lower conductive pattern and the upper conductive pattern, and a plurality of conductive plugs, disposed on parts of the cross regions, electrically connecting to the lower conductive pattern and the upper conductive pattern.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a test key array on a wafer,and more particularly, to a test key array on a wafer for waferacceptable test (hereinafter abbreviated as WAT).

2. Description of the Prior Art

In the standard semiconductor process, in order to evaluate theefficiency of each procedure and to confirm performance of the elementsafter the procedures, a WAT is performed on the wafers. The WAT includesan electrical test on the test pad structure disposed around theperipheral regions of the dice. And by analyzing the feedback signal,the stability of the semiconductor processes is confirmed as well as thecharacteristics and performance of each device of the dice.

Prior to the WAT, test keys are formed in the scribe lines around thedice. A device formed in a die is usually for logic computation or formemory, while a similar device is also formed in the scribe line as apart of the test key. The state-of-the-art also provides test padselectrically connected to the test keys. Accordingly, the test keys areelectrically connected to an external circuit or probes of a probe cardthrough the test pads to check the quality of the IC process in the WAT.After the WAT, a dicing process is performed to individualize each dieon the wafer.

A dual damascene process is a method of forming a conductive wirecoupled with a via plug in a dielectric layer. The dual damascenestructure, comprising an upper wire and a lower via plug, is used toconnect devices and wires in a semiconductor wafer and is insulated withother devices by the inter-layer dielectrics (ILD) around it. With theprogress of the semiconductor fabrication and the miniaturization of thedevices, size of the die and width of the scribe lines are consequentlyshrunk. Therefore, the dual damascene structure may make it easier tocontact others devices or wires when some manufacturing defects occur,such as the over-etching defect or the misalignment defects. FIGS. 1Aand 1B are schematic diagrams showing an over-etching issue happening ina dual damascene structure. As shown in FIG. 1, a via plug 1 is disposedin a dielectric layer 2, and electrically connected to a lower metallayer M1 and an upper metal layer M2, and especially connects the traceM1B of the lower metal layer M1, but does not contact the adjacenttraces M1 or M1C directly. However, when an over-etching issue happens,as shown in FIG. 1B, the via plug 1 may contact the adjacent traces, andthe issue mentioned above can happen more easily when the size of thedie and width of the scribe lines are consequently shrunk.

SUMMARY OF THE INVENTION

The present invention provides a test key array comprising a lowerconductive pattern, wherein the lower conductive pattern includes aplurality of first L-shaped traces parallel to each other, an upperconductive pattern, wherein the upper conductive pattern includes aplurality of second L-shaped traces parallel to each other. In addition,the lower conductive pattern crosses to the upper conductive pattern,and a plurality of cross regions are defined between the lowerconductive pattern and the upper conductive pattern. A plurality ofconductive plugs, disposed on parts of the cross regions, electricallyconnect to the lower conductive pattern and the upper conductivepattern.

The present invention further provides a test key array comprising alower conductive pattern, wherein the lower conductive pattern includesa plurality of first L-shaped traces parallel to each other, an upperconductive pattern, wherein the upper conductive pattern includes aplurality of second L-shaped traces parallel to each other. In addition,the lower conductive pattern crosses to the upper conductive pattern,and a plurality of cross regions are defined between the lowerconductive pattern and the upper conductive pattern, and at least one ofthe cross region includes a conductive plug array disposed thereon. Eachconductive plug array includes a plurality of conductive plugs,electrically connecting to the lower conductive pattern and the upperconductive pattern.

The present invention provides a test key array, and the test key arrayhas a novel structure, especially comprising a plurality of firstL-shaped traces and a plurality of second L-shaped traces crossed toeach other, and a plurality of conductive plugs electrically connectingto the lower conductive pattern and the upper conductive pattern.Therefore, the user can determine whether the defects such as themisalignment or the over-etching occur or not in the vertical directionand in the horizontal direction simultaneously by detecting the firstpad and the second pad.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams showing an over-etching issuehappening in a dual damascene structure.

FIG. 2 is a top view diagram showing the test key array of the firstpreferred embodiment of the present invention.

FIG. 3 is a cross section diagram along the cross line A-A′ in FIG. 2.

FIG. 4 is a top view diagram showing the test key array of anotherembodiment of the present invention.

FIG. 5 is an example showing the test key applied in a multiple layerstacked structure.

FIG. 6 is a top view diagram showing the test key array of the secondpreferred embodiment of the present invention.

DETAILED DESCRIPTION

To provide a better understanding of the present invention to usersskilled in the technology of the present invention, preferredembodiments are detailed as follows. The preferred embodiments of thepresent invention are illustrated in the accompanying drawings withnumbered elements to clarify the contents and the effects to beachieved.

Please note that the figures are only for illustration and the figuresmay not be to scale. The scale may be further modified according todifferent design considerations. When referring to the words “up” or“down” that describe the relationship between components in the text, itis well known in the art and should be clearly understood that thesewords refer to relative positions that can be inverted to obtain asimilar structure, and these structures should therefore not beprecluded from the scope of the claims in the present invention.

FIG. 2 is a top view diagram showing the test key array of the firstpreferred embodiment of the present invention. As shown in FIG. 2, thetest key 3 comprises a lower conductive pattern 10, wherein the lowerconductive pattern 10 includes a plurality of first L-shaped traces 12parallel to each other; an upper conductive pattern 20, wherein theupper conductive pattern 20 includes a plurality of second L-shapedtraces 22 parallel to each other, wherein in this embodiment, eachsecond L-shaped trace 22 is an “up-side-down L shaped structure”.Therefore, the lower conductive pattern 10 crosses to the upperconductive pattern 20, and a plurality of cross regions 30 are definedbetween the lower conductive pattern 10 and the upper conductive pattern20.

Besides, FIG. 3 is a cross section diagram along the cross line A-A′ inFIG. 2. As shown in FIG. 3, the lower conductive pattern 10 and theupper conductive pattern 20 are disposed on different levels, and thetest key array 3 of the present invention further comprises a pluralityof conductive plugs 40, disposed on parts of the cross regions 30,electrically connecting to the lower conductive pattern 10 and the upperconductive pattern 20. In other words, in the present embodiment, thereis a plurality of cross regions 30 arranged in a matrix, but only partsof these cross regions 30 have conductive plugs 40 disposed thereon.More precisely, in the present invention, if one cross region has oneconductive plug 40 disposed thereon (such as the cross region A shown inFIG. 2), other cross regions 30 adjacent to the cross region A,especially the cross regions 30 disposed on two sides of the crossregion A along the X-axis and the Y-axis, do not comprise any conductiveplugs 40. In short, when viewed in top view, the conductive plugs 40 arearranged like a “checkerboard”.

In addition, the present invention further comprises a first pad 50 anda second pad 60, electrically connecting to the lower conductive pattern10. The first pad 50 and the second pad 60 are metal pads or others padsmade of conductive materials. The first pad 50 and the second pad 60 canbe used for electrically connecting to the probes for detecting signalsfrom the test key array. In the present embodiment, if one firstL-shaped traces 12 is electrically connected to the first pad 50, theother first L-shaped traces 12 adjacent to the one first L-shaped traces12 will be electrically connected to the second pad 60. More precisely,the lower conductive pattern 10 comprises a plurality of first L-shapedtraces 12 parallel to each other, each first L-shaped trace 12 whichelectrically connects to the first pad 50 is disposed between two firstL-shaped traces 12 which electrically connect to the second pad 60, andsimilarly, each first L-shaped trace 12 which electrically connects tothe second pad 60 is disposed between two first L-shaped traces 12 whichelectrically connect to the first pad 50.

In the present invention, please refer to FIGS. 2˜3, when viewed in topview, the test key has two regions: region V and region H, wherein theregion V is used for detecting the misalignment or the over-etchingissues occurring in the vertical direction (Y-axis), and the region H isused for detecting the misalignment or the over-etching issues occurringin the horizontal direction (X-axis). Take FIG. 3 as an example, asshown in FIG. 3, the conductive plugs 40 are disposed on the firstL-shaped traces 12 which electrically connect to the second pad 60.Since the conductive plugs 40 does not contact the first L-shaped traces12 which electrically connected to the first pad 50, the first pad 50cannot detect any signal in a normal case. However, if some defects likethe over-etching (such as the defects shown in FIG. 1B), themisalignment or the blind hole, wherein a blind hole refers to a holethat is etched, but without breaking through to the other side of thelayer, occur in the vertical direction, the conductive plug 40 may notonly contact the first L-shaped traces 12 which electrically connect tothe second pad 60, but also contacts the first L-shaped traces 12 whichelectrically connect to the first pad 50. In that case, the first pad 50may detect some signals. So the user can determine whether the defectssuch as the misalignment and the over-etching occur or not in thevertical direction by detecting the first pad 50 and the second pad 60.Similarly, within the region H, the user can determine whether thedefects mentioned above occur or not in the horizontal direction bydetecting the first pad 50 and the second pad 60 too. In the presentinvention, the user may determine whether the defects such as themisalignment or the over-etching occur or not in the vertical directionand in the horizontal direction simultaneously by detecting the firstpad 50 and the second pad 60, and if combining with other detectingmethods, such as the measuring the potential drop or the currents, theuser can further determine in which direction the defects occurred.

In the embodiment mentioned above, the first pad 50 and the second pad60 are electrically connected to the lower conductive pattern 10, butthe present invention is not limited thereto, in other preferredembodiment of the present invention, the first pad 50 and the second pad60 may also electrically connect to the upper conductive pattern 20, andit should be comprised in the scope of the present invention.

In the embodiment mentioned above, if one cross region has oneconductive plug 40 disposed thereon (such as the cross region A shown inFIG. 2), other cross regions 30 adjacent to the cross region A,especially the cross regions 30 disposed on two sides of the crossregion A along the X-axis and the Y-axis, do not comprise any conductiveplugs 40. In short, when viewed in top view, the conductive plugs 40 arearranged like a “checkerboard”. However, in another embodiment of thepresent invention, FIG. 4 is a top view diagram showing the test keyarray of another embodiment of the present invention. As shown in FIG.4, the conductive plugs 40 are disposed on every adjacent cross region30. More precisely, within the region V, the conductive plugs 40 aredisposed on disposed on every cross region 30 along the X-direction, andwithin the region H, the conductive plugs 40 are disposed on disposed onevery cross region 30 along the Y-direction.

The test key array of the present invention can be a stacked structure.For example, please refer to FIG. 5. FIG. 5 is an example showing thetest key applied in a multiple layer stacked structure. The structure ofthe test key 4 is similar to the test key 3 (shown in FIG. 2) mentionedabove, but the test key 4 is a multiple layer stacked structure, furthercomprising a plurality of conductive plugs 40′ disposed on the upperconductive pattern 20. It is worth noting that each conductive plugs 40′is not disposed “right above” the conductive plugs 40 disposed below.And another conductive pattern (not shown) is disposed on the conductiveplugs 40′ and the upper conductive pattern 20 to form the multiple layerstacked structure.

Preferably, in the manufacturing process for forming the test key of thepresent invention, the second L-shaped traces 22 and the conductiveplugs 40 are formed monolithically. In other words, the second L-shapedtraces 22 and the conductive plugs 40 are formed simultaneously andcomprise the same material. Besides, the thickness of each secondL-shaped trace 22 is preferably larger than the thickness of each firstL-shaped trace 12, in addition, the first L-shaped traces 12 and thesecond L-shaped traces 22 preferably comprise copper traces, but thepresent invention is not limited thereto.

Please refer to FIG. 6, FIG. 6 is a top view diagram showing the testkey array of the second preferred embodiment of the present invention.In this embodiment, the upper conductive pattern 20 comprises aplurality of second L-shaped traces 22 parallel to each other, and eachsecond L-shaped trace 22 of the upper conductive pattern 20 has twoterminal regions D, and the width of the second L-shaped trace 22 withinthe terminal region D is larger than other widths of the second L-shapedtraces 22. Besides, the arranged direction of the second L-shaped traces22 is parallel to the arranged direction of the first L-shaped traces 12within the terminal region D. Therefore, the second L-shaped trace 22has larger area within the terminal region D. In this embodiment, eachterminal region may comprise a conductive plug array 70 or only oneconductive plug 40, wherein each conductive plug array 70 includes aplurality of conductive plugs 40. More precisely, in the first preferredembodiment mentioned above, if one cross region 30 has the conductiveplug 40 disposed thereon, this cross region 30 comprises only oneconductive plug 40 disposed thereon, but in this embodiment, theterminal region D comprises a plurality of conductive plugs 40 disposedthereon. In the general situation, the over-etching defect is morelikely to occur during manufacturing process for forming the conductiveplug array than forming only one conductive plug. Therefore, in thisembodiment, the terminal region D has a larger area, for accumulating aplurality of conductive plugs 40 (the conductive plug array 70), so asto detect whether the defects, such as over-etching, will occur or notwhen forming the conductive plug array 70. The other components,material properties, and manufacturing method of the test key array aresimilar to those of the first preferred embodiment detailed above andwill not be redundantly described.

In summary, the present invention provides a test key array, and thetest key array has novel structure, especially comprising a plurality offirst L-shaped traces and a plurality of second L-shaped traces crossedto each other, and a plurality of conductive plugs electricallyconnecting to the lower conductive pattern and the upper conductivepattern. Therefore, the user can determine whether the defects such asthe misalignment or the over-etching occur or not in the verticaldirection and in the horizontal direction simultaneously by detectingthe first pad and the second pad.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A test key array, comprising: a lower conductivepattern, wherein the lower conductive pattern includes a plurality offirst L-shaped traces parallel to each other; an upper conductivepattern, wherein the upper conductive pattern includes a plurality ofsecond L-shaped traces parallel to each other, wherein, the lowerconductive pattern crosses to the upper conductive pattern, and aplurality of cross regions are defined between the lower conductivepattern and the upper conductive pattern; and a plurality of conductiveplugs, disposed on parts of the cross regions, electrically connectingto the lower conductive pattern and the upper conductive pattern,wherein the second L-shaped traces and the conductive plugs are formedmonolithically.
 2. The test key array of claim 1, wherein the lowerconductive pattern and the upper conductive pattern are disposed ondifferent levels.
 3. The test key array of claim 1, further comprising afirst pad and a second pad, electrically connecting to the lowerconductive pattern.
 4. The test key array of claim 3, wherein one firstL-shaped trace of the lower conductive pattern is electrically connectedto the first pad, and the other first L-shaped traces adjacent to thefirst L-shaped trace are electrically connected to the second pad. 5.The test key array of claim 1, wherein one cross region has theconductive plug disposed thereon, and the other cross regions adjacentto the one cross region do not have conductive plugs disposed thereon.6. The test key array of claim 1, wherein one cross region has theconductive plug disposed thereon, and only one conductive plug on thecross region.
 7. The test key array of claim 1, wherein each secondL-shaped trace of the upper conductive pattern has two terminal regions,and the width of the second L-shaped trace within each of the twoterminal regions is larger than other widths of the second L-shapedtraces.
 8. The test key array of claim 7, wherein an arranged directionof the second L-shaped traces is parallel to an arranged direction ofthe first L-shaped traces within the terminal region.
 9. The test keyarray of claim 1, wherein the thickness of each second L-shaped trace islarger than the thickness of each first L-shaped trace.
 10. The test keyarray of claim 1, wherein the first L-shaped traces and the secondL-shaped traces comprise copper traces.
 11. A test key array,comprising: a lower conductive pattern, wherein the lower conductivepattern includes a plurality of first L-shaped traces parallel to eachother; an upper conductive pattern, wherein the upper conductive patternincludes a plurality of second L-shaped traces parallel to each other,wherein, the lower conductive pattern crosses to the upper conductivepattern, and a plurality of cross regions are defined between the lowerconductive pattern and the upper conductive pattern; and at least one ofthe cross regions includes a conductive plug array disposed thereon, andeach conductive plug array includes a plurality of conductive plugs,electrically connecting to the lower conductive pattern and the upperconductive pattern.
 12. The test key array of claim 11, wherein thelower conductive pattern and the upper conductive pattern are disposedon different levels.
 13. The test key array of claim 11, furthercomprising a first pad and a second pad, electrically connecting to thelower conductive pattern.
 14. The test key array of claim 13, whereinone first L-shaped trace of the lower conductive pattern is electricallyconnected to the first pad, and the other first L-shaped traces adjacentto the first L-shaped trace are electrically connected to the secondpad.
 15. The test key array of claim 11, wherein one cross region hasthe conductive plug disposed thereon, and the other cross regionsadjacent to the one cross region do not have conductive plugs disposedthereon.
 16. The test key array of claim 11, wherein the second L-shapedtraces and the conductive plugs are formed monolithically.
 17. The testkey array of claim 11, wherein each second L-shaped trace of the upperconductive pattern has two terminal regions, and the width of the secondL-shaped trace within each of the two terminal regions is larger thanother widths of the second L-shaped traces.
 18. The test key array ofclaim 17, wherein an arranged direction of the second L-shaped traces isparallel to an arranged direction of the first L-shaped traces withinthe terminal region.